1. Field of the Invention
The present invention relates to communication devices and in particular, analog to digital converters used in communication devices.
2. Description of the Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. Wireless communication systems include Wireless Local Area Networks, Wireless Personal Area Networks, cellular communication systems, satellite communication systems, 60 GHz standards, Near Field Communications, and Infrared Communications, among others. Wired communication systems include Wide Area Networks, Local Area Networks, the Internet, and the World Wide Web, among others.
Powerline communication (PLC) is a technology that encodes data in a signal and transmits the signal on existing electricity powerlines in a band of frequencies that are not used for supplying electricity. Accordingly, PLC leverages the ubiquity of existing electricity networks to provide extensive network coverage. Furthermore, since PLC enables data to be accessed from conventional power-outlets, no new wiring needs to be installed in a building (or different parts of a building). Accordingly, PLC offers the additional advantage of reduced installation costs. Communications within the household or within other premises may also be serviced other communication techniques as well.
All communication devices include similar components, including an Analog Front End (AFE) and a Digital Front End (DFE). The AFE processes analog communication signals and couples the analog communication signals to and from an antenna, media, etc. The DFE processes digital communication signals and interfaces with host processing circuitry. Analog to Digital Converters (ADCs) and Digital to Analog Converters (DACs) inter couple the DFE and the AFE and convert the communication signals between an analog format and a digital format.
Modern communication devices place great demands on the ADCs and DACs. In particular, ADCs are required to sample analog communication signals across wide frequency bands to produce corresponding digital communication signals. This is increasingly difficult to achieve with a single ADC, so to address this problem, one solution is to combine the use of multiple individual ADCs that sample the analog communication signals in a time divided manner and then combine the multiple digitized signals produced by the multiple individual ADCs. Time synchronization of the multiple individual ADCs is highly susceptible to timing and phase errors, which grows more problematic with wider frequency band servicing. In wide-band environments such as in PLC communications, timing and phase error correction circuits that are required for correcting the timing and phase errors occupy about the same area as that of the core ADC elements. The timing and phase error correction circuits produce heat, consume power, and increase the size of the Integrated Circuit in which they reside. Further, while this time divided ADC structure may provide benefits in some communication devices, e.g., Coaxial tuners, it is less beneficial for other communication devices, e.g., PLC devices.